Nuances of triple triangle- Mtbr.com
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  1. #1
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    Nuances of triple triangle

    I'm most of the way through a frame at the moment, only seatstays left. I'm very tempted to triple triangle it! I haven't built a frame like that before, are there any things to be aware of?

    I have more than enough butt on the top tube to get it done, and the seatstays are long enough.

    Thanks

  2. #2
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    I built my first frame of this type way back in 1982. This was in the period of the traditional horizontal top tube. Also, tubing of the day was 1" TT and seat tubes were 1 1/8". The most notable enhancement that happened was that the frame became much stiffer and resisted lateral flex much more than a typical Road frame of that time. This is due to the intersecting tubes shortening the effective length of both ST and TT. This means that a TT of 600mm intersected at 150mm had only 450mm of lateral flex which combined with a shortened ST changed the load pathways through that area.
    In todays world of over-sized tubing options, you can opt out of this design style, but if you like it, go ahead, it will not yeild a negative result.

    Eric
    If I don't make an attempt, how will I know if it will work?

  3. #3
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    awesome, thanks for the info

    Do you know if i should be particularly worried about HAZ etc? Im tig welding, at this point im very confident behind the torch and can control the heat effectively, however i'm still wary of not creating some vast weak spot.

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    Something that I should add here is to watch for ovalizing of the Seat Tube where the heat has been applied in the welding process. A reamer will help after the fact.

    Eric
    If I don't make an attempt, how will I know if it will work?

  5. #5
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    Quote Originally Posted by Eric Malcolm View Post
    Something that I should add here is to watch for ovalizing of the Seat Tube where the heat has been applied in the welding process. A reamer will help after the fact.

    Eric
    Yah i would be careful not to land the SS's on the butted portion of the ST. Did that once; had to ream the heck out of it and eventually it cracked there (poor heat control also partially to blame). I won't do another triple triangle frame (i only see downsides) but if i did i'd use a straight gauge seat tube or 2 sleeves on the ST.

    Also gotta be careful to land the SS's on the thick part of the TT. This probably should have been a design decision that was made with the frame was initially designed.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

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